<!DOCTYPE html>
<html lang="zh">
<head>
    <meta charset="UTF-8">
    <title>08-上下margin折叠_03-无内容块级元素</title>
    <style>
        .div1 {
            background-color: #f00;
            margin-top: 60px;
            margin-bottom: 100px;
        }
    </style>
</head>
<body>
666
<div class="div1"></div>
<div class="div1"></div>
<div class="div1"></div>
<div class="div1"></div>
777
</body>
</html>